Free tools and guides for the people turning data into decisions.
Practical utilities, sharp guides, and resources we use ourselves — gathered in one place.
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Sample Size Calculator
Plan honest experiments with the right statistical power. Confidence level, margin of error, population proportion — done in seconds.
Drop your conversions in, get a clean read.
Paste raw signups + activity, get the matrix.
Paste funnel counts, get the weakest steps.
Reads from the team.
Field notes from the people running the cohorts, shipping the code, and reviewing your work.
What every analyst should have installed and why.
A field guide to retrieval-augmented generation in production.
How to design pricing tests that deliver decisions, not vibes.
Reliability, observability, and human-in-the-loop patterns.
Templates we've used to break bad-news quarters cleanly.
What to test, what to skip, and what to ignore.
Printable references for the real work.
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